The words colonel, kernel sound the same but have different meanings and spellings. Why do colonel, kernel sound the same even though they are completely different words?
The answer is simple: colonel, kernel are homophones of the English language.
A commissioned rank in the U.S. Army, Air Force, or Marine Corps that is above lieutenant colonel and below brigadier general.
One who holds this rank or a similar rank in another military organization.
An honorary nonmilitary title awarded by some states of the United States.
A grain or seed, as of a cereal grass, enclosed in a husk.
The inner, usually edible seed of a nut or fruit stone.
The most material and central part; the core: "that hard kernel of gaiety that never breaks” ( Evelyn Waugh).
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.